Line cards which connect to backplanes typically include levers that, when rotated by technicians, enable the technicians to operatively connect the line cards with the backplanes, and disconnect the line cards from the backplanes. In particular, when a technician inserts a line card into a card cage and then rotates the levers of line card toward the card cage, the ends of the levers grab the card cage and evenly guide the line card into connection with a backplane at the back of the card cage. Furthermore, when the technician rotates the levers of line card away from the card cage, the ends of the levers push against the card cage and evenly disconnect the line card from the backplane.
It should be understood that a variety of movements in card cage environments have the potential to disconnect line cards from the backplanes. For example, vibration from fan assemblies can inadvertently dislodge a connected line card from a backplane over an extended period of operation. As another example, a technician who has opened a cabinet door or panel to provide servicing of another system component could accidentally actuate a lever and release a line card from its connected position within the card cage. In particular, a dangling sleeve, a stray cable or a fast moving limb could catch on a lever and inadvertently disengage the line card while the system is in operation.
To prevent line cards from inadvertently disconnecting from the backplane, some manufacturers equip their line cards with thumbscrews which are configured to thread into screw holes of the card cages. Along these lines, once a technician has properly connected such a line card to a backplane by closing the levers in a direction toward the card cage, the technician turns the thumbscrews of the line card in order to secure the line card to the card cage. As a result, any vibration or inadvertent actuation of a lever will not extract the line card from its installed position relative to the backplane.